Bangladesh University of Engineering and Technology
EEE 201
Electronics I
Diode
BUET Bangladesh University of Engineering and Technology
Diodes
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
Forward Bias Region:
Is is called the saturation current or scale current. This current
depends on physical properties of the diode- temperature,
operating conditions etc. It is called scale current because, it
is proportional to the area of the diode. The higher the crosssectional area, the higher the current flow through the diode,
the higher scale current we get. The value of saturation
current doubles for 5 degrees rise in temperature.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
Forward Bias Region:
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
The term n depends on the material and the structure of the
diode. The diodes that are used in integrated circuits, have n
equal to 1. Unless otherwise specified, we will be using n
value equal to 1.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes
i1  Is(e
v1
nV T
)
v1  nVT ln(i1 / Is)
v2  nVT ln(i2 / Is)
v2  v1  nVT ln(i2 / i1 )
If i1 is about 10 times of i1, we see that to increase
current by 10 times approximately, we need a voltage
increment of 2.3nVT. Which is approximately 0.12V for
n=1.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clipper
• Series Clipper Circuit
• Depending on models used the
response of the circuit will vary.
• For ideal diode model, the diode is
considered short circuited in forward
bias mode.
• In reverse bias, the diode is open
circuited.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clipper
• Use ideal diode model
• What will be the
voltage across R?
• For other models like
constant voltage drop
model, we need to consider
another 0.7V drop for the
diode itself
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clipper
This time the diode is in series configuration
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clipper
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clamper
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Clampers
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Rectifier
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Rectifier
•
•
•
•
•
The diode would conduct only for a brief period of time
near the peak of the signal.
The diode starts conduction at t1 and stops conduction at
t2.
When the diode is off, the capacitor discharges through the
resistor in an RC circuit. The discharging interval lasts for
the entire period. At the end of discharging period,Vo=Vp-Vr.
When the ripple voltage is small, the output voltage is
almost constant and becomes equal to the peak voltage of
input signal.
The time constant should be very high.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Rectifier
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Zener Diode
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Zener Diode
• Designed for operation in reverse bias
region.
• Totally different physics of conduction
in reverse bias conduction.
• Slightly lower breakdown voltage than
conventional diode.
• Suited for operation in reverse
breakdown mode.
• Similar physics of current conduction
in forward bias region.
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Zener Diode
Voltage Shifter
Voltage Regulator
EEE 201: Electronics I
BUET Bangladesh University of Engineering and Technology
Diodes: Zener Diode
EEE 201: Electronics I